VB.NET编写OPC客户端，添加组报错！

[dragonxue]

代码如下，运行到add group报错，但是重复运行到第3次就正常了，每次都是第三次就正常了，不知道什么原因？

 '===============connect======================================
        If ConnectedOPCServer Is Nothing Then
            Try
                ConnectedOPCServer = New OPCAutomation.OPCServer
                ConnectedOPCServer.Connect(ServerName.Text, )

            Catch ex As Exception
                ConnectedOPCServer = Nothing
                MessageBox.Show("OPC server connect failed with exception: " + ex.Message, "connect error", MessageBoxButtons.OK)
            End Try
        End If
        '================add group====================================================
        If Not ConnectedOPCServer Is Nothing And ConnectedGroup Is Nothing Then
            Try
                ConnectedOPCServer.OPCGroups.DefaultGroupIsActive = True
                ConnectedGroup = ConnectedOPCServer.OPCGroups.Add("Group1")
                ConnectedGroup.UpdateRate = Val(1000)
                ConnectedGroup.IsSubscribed = True

            Catch ex As Exception
                ConnectedGroup = Nothing
                MessageBox.Show("OPC server add group failed with exception: " + ex.Message, "add group error", MessageBoxButtons.OK)
            End Try
        End If
        '============add items==================================================
        If Not ConnectedGroup Is Nothing Then
            Try
                Dim ItemCount As Integer = 1
                Dim AddItemServerErrors As System.Array

                OPCItemIDs(1) = OPCItemName(1).Text
                ClientHandles(1) = 1

                ConnectedGroup.OPCItems.DefaultIsActive = True
                ConnectedGroup.OPCItems.AddItems(ItemCount, OPCItemIDs, ClientHandles, ItemServerHandles, AddItemServerErrors)

            Catch ex As Exception
                MessageBox.Show("OPC server add items failed with exception: " + ex.Message, "add items error", MessageBoxButtons.OK)
            End Try
        End If

[yishumei]

楼主，错误内容截个图看看